Computer systems, including servers and storage subsystems, use significant amounts of power. In the past, conserving power has always been secondary to speed and processor availability. However, Internet sites with excess capacity for high peak periods such as an Olympics website or an online stock trading website waste power keeping the computer systems ready for the next peak period. In addition, power problems and rolling blackouts, such as those experienced in California in 2000-2001 during deregulation, have begun to spur awareness that power conservation may be required in order to keep a network center operational. In addition, as microprocessors continue to scale up in speed and density, corresponding power consumption may increase dramatically requiring more efficient power management.
Because of the increased processing demands required by today's software and Internet sites, more computer systems utilize multi-processor systems which require more power to operate than single processor computer systems. In addition, the multi-processor computer systems generally have multiple power supplies to power the multi-processors and provide redundancy features. In multi-processor technology, multi-processor specifications often describe how to start and stop processors in multi-processor servers. The multi-processor specifications select a boot processor and then add application processors as discovered, so that a multi-processor server is dynamically configured without a fixed foreknowledge of the number of processors in the server. But the multi-processor and the Advanced Configuration and Power Interface (“ACPI”) specifications do not typically allow for any power consumption control or savings from a source or decision engine external to the server unit in which the multiple processors reside nor do the specifications typically provide for strategic control over the multiple power supplies.
With the advent of power hungry processors and multi-processor computer systems, power management has become more important. In addition, powering up and down the multi-processors imposes inrush loads and efficiency changes in the power supplies. For instance, power supplies may fail during startup, when inrush currents stress the power supply components. Therefore, the power supplies must be able to manage the inrush load without failing and yet efficiently supply a steady state current to the multi-processors and other computer components. The power supplies also must continue to provide appropriate redundancy for the computer system while optimizing power consumption. Power supply management, sequencing, and conservation requires meeting not only inrush and steady state load demands but also policy based redundancy and efficiency requirements. Demand triggered power supplies have attempted to reduce power consumption by starting up additional power supplies based upon the load on the computer system but they do not generally account for inrush supply, choose the most efficient power supply to start from a pool of available power supplies, or provide for enterprise wide power conservation.